Truss-bridge



'UNITED STATES PATENT OFFICE.

JOHN C. BRIGGS, OF CONCORD, NEW HAMPSHIRE.

TRUSS-BRIDGE.

Specification of Letters Patent No. 22,106, dated November 23, 1858..

To all whom t may concern:

Be it known that I, JOHN C. Braces, of Concord, in the county ofMerrimack and State of New Hampshire, have invented a new and Improvedode of Giving Elasticity to the Compressed Joints of Truss- Frames; andI do hereby declare that the following is a full and exact descriptionthereof, reference being had to the accompanying drawings and theletters of reference marked thereon.

My invention consists in the application of springs to the bearings ofeither the posts, main braces, counter braces, iron rods of alldescriptions, or to any compressed joint in trusses constructed, eitherof wood, iron, or wood and iron combined. The most convenient andavailable material for these springs is india rubber. The shape mostgenerally required is the same as that of the ordinary india rubbercar-springs of the market; that is, short solid cylinders, with holesthrough their centers, as represented by Figure 4. This is the shapemost suitable for iron rods. Those for other compressed joints may be ofa size and shape to suit the particular size and shape of the adjacentsurfaces. The place of application of these springs in ordinary wood andiron truss-frames is most convenient, as represented by the drawings;that is, generally under the washers of the iron rods, as S. S. S. Figs.l, 2 and 3.

Panels l and 2, of Fig. l, represent a side vie-w of a Pratttruss-frame, and panels 3 and 4 the same of a Howe truss. Fig. 9.represents a truss beam. Fig. 3 represents an arch combined with a trussframe, in which the diierent panels show some of the various differentmodes in use of arranging the diagonal supports.

S. S. S. are the points whe-re I think the springs may generally be mosteconomically applied. E. E. E. are points where the springs might beapplied with similar effects. The application at one point in the panelis considered to be generally suliicient. It may, however, be sometimesdesirable to apply it at several.

I have intended to represent by the drawing, the leading features of allthe truss frames in use, and thus to show the applicability of myinvention to all truss frames. There result from its use the followingadvantages:

l. The truss-frame is rendered more elastic, and therefore less liableto be broken by al sudden strain, such as would be caused by the impactof a falling body. For the same reason the durability of trussed bridgesand other trussed structures is increased, by lessening the effects ofthe constant jar and violent concussions to which they are eX- posed.This is true of trusses made of any kind of material, as all wood, alliron, or both combined.

2. The springs of themselves (by having them previously tested andgaged) serve as dynamometers, by which the strains upon different partsof a truss can be more accurately ascertained and more correctlyproportioned. This is especially desirable when two systems arecombined, as an arch and truss frame. Fig. 3 shows an instance of this.

3. Unequal contraction and expansion of different parts of the sametruss, from change of temperature, can take place without doing violenceto each other, or making loose joints. The thickness of the springsshould be such as to give suliicient elasticity for this purpose.

4. The springs show when the strain produced by a counter-rod or braceupon a main rod or brace is equivalent to a given load, thus making itpracticable so to load any trussed structure, by means of counters, thatit shall remain inflexible under the maximum load admissible thereon.They enable this desirable quality in trusses to be gained, with greatersafety than it is now done.

lV hat I claim as my invention, and desire to secure by Letters Patent,is-

The application of india rubber, or equivalent springs, to thecompressed joints of truss frames and truss beams, substantially in themanner and for the purposes described above.

JOHN C. BRIGGS. lVitnesses P. S. CHANDLER, JOHN A Bor'r.

